1. Field of the Invention:
This invention relates to an endoscope TV camera apparatus provided with an automatic gain controlling means for automatically controlling a characteristic difference between respective divided image signal processing circuits.
2. Description of the Related Art:
An endoscope apparatus for displaying an image of an object by connecting a TV camera to an eyepiece part of an endoscope (such as a fiber scope) is well-know. In the case of a fiber scope, such TV camera is used for imaging an optical image of an object transmitted to an eyepiece part through an image guide fiber within the scope.
In an endoscope apparatus of the above mentioned TV camera wherein a color image is simultaneously imaged by radiating a white radiating light to an object, a three-plate type TV camera is generally used. In such three-plate type TV camera, a three-color analyzing prism (dichroic prism) is provided in the rear of an imaging lens, a white radiating light is divided into three color lights of primary colors of R, G and B and the respective color lights are imaged by separate solid state imaging devices. With such three-plate type TV camera, the respective color signals can be independently processed and the colors can be also independently corrected so that a color image of an object having good tone and high resolution may be obtained.
However, with a conventional three-plate type TV camera, it has heretofore been impossible to automatically control a gain adjustment in gain controlling amplifiers (abbreviated as GCA's hereinafter) for amplifying respective divided signals and inputting them into signal processing circuits, because it is necessary to provide respective automatic gain controlling means (abbreviated as AGC means hereinafter) for the GCA's for the respective color signals and therefore it is difficult to uniformly control the respective GCA's by the AGC means.
In the above mentioned GCA and signal processing circuit, generally a dispersion will be produced between the respective circuits and a characteristic difference will be generated between the respective signals. Also, a characteristic difference will be generated by a variation in the lapse of time. Therefore, there will occur such problems that the correlation of respective color signal levels will collapse and particularly the color reproducing characteristic will deteriorate.